THYROIDAL ENHANCEMENT OF RAT MYOCARDIAL NA,K-ATPASE - PREFERENTIAL EXPRESSION OF ALPHA-2 ACTIVITY AND MESSENGER-RNA ABUNDANCE
THYROIDAL ENHANCEMENT OF RAT MYOCARDIAL NA,K-ATPASE - PREFERENTIAL EXPRESSION OF ALPHA-2 ACTIVITY AND MESSENGER-RNA ABUNDANCE
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DOI：
10.1007/bf01868642
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发表时间：
1990-05-01
影响因子：
2.4
通讯作者：
ISMAILBEIGI, F
中科院分区：
文献类型：
--
作者：
GICK, GG;MELIKIAN, J;ISMAILBEIGI, F
In hypothyroid rat myocardium, the low-ouabain-sensitivity Na,K-ATPase activity had a KI = 10-4 M and accounted for .apprx. 95% of the enzyme activity, while the high-ouabain-sensitivity activity contributed .apprx.5% to the total activity, with a KI = 3 .times. 107 M. mRNA.alpha.1 was 7.2 and 5.5-fold more abundant than mRNA.alpha.2 and mRNA.beta., respectively, in hypothyroid ventricles while mRNA.alpha.3 was undetectable. Administration of T3 increased total NaK-ATPase activity 1.6-fold; the low-ouabain-sensitivity activity increased 1.5-fold while high-ouabain-sensitivity activity was stimulated 3.2-fold. T3 increased the number of high-affinity ouabain-binding sites 2.9-fold with no change in Kd (.apprx.2 .times. 10-7 M). The abundances of mRNA.alpha.1, mRNA.alpha.2, and mRNA.beta. (per unit RNA) following T3 treatment increased 3.6-, 10.6-, and 12.7-fold, respectively. The larger increments in subunit mRNA abundances than in Na,K-ATPase activity suggests that involvement of translational and/or post-translational regulatory steps in Na,K-ATPase biogenesis in response to T3. It is concluded that T3 enhances myocardial Na,K-ATPase subunit mRNA aubndances and Na,K-ATPase activity, and that the expression of the high- and low-ouabain-sensitivity activities are probably a reflection of the abundances of the .alpha.2 and .alpha.1 isoforms, respectively. The physiological role played by the .beta. subunit remains uncertain.
